The invention relates generally to four-wheel drive vehicles in which relative rotation occurs between the front and rear differentials with respect to their common input shaft axis and more particularly to a four-wheel drive tractor in which this relative rotation is eliminated by longitudinally extending drive gearing to the wheels from the differential coupled with a laterally extending walking beam suspension connected to the wheels.
In the past, four-wheel drive tractors were articulated around a vertical axis to provide steering control and the front axle and differential were free to oscillate around a longitudinal axis to keep all four wheels on the ground over rough, uneven terrain. This configuration permits relative rotation of the front and rear differentials and results in the relative rotation due to traversing rough terrain to be imparted as high impact shock torques on the drive train. These high shock torques often result in premature failures of the drive train and generally uneven power transmission from the engine to the drive wheels.